The present invention is particularly applicable for the liquid treatment of workpieces at one station of a multiple-station treating cycle, such as a chemical, electrochemical and electroplating processing cycle, for example. It is conventional in treating processes of the foregoing type to subject the workpieces to various preliminary cleaning and pretreatments prior to the prescribed chemical treatment, such as electroplating, followed thereafter by one or more post-treatments. It is generally necessary to subject the workpieces to a plurality of aqueous rinse treatments between the pre-treatment, electroplating and post-treatment phases to minimize contamination of the several treating solutions by residual treating solutions carried-over from the preceding treating station.
It is usually preferred to subject the workpieces to at least two and preferably three or more individual water rinse treatments in a counterflow manner to reduce the quantity of residual treating solution on the workpiece to a level at which only a small degree of carry-over to adjacent treating stations occurs. It will be appreciated that such a plural rinse treatment in accordance with prior art practices has necessitated an individual treating station for each rinse solution, substantially increasing the length of the processing line and the amount of plant space required for a desired production capacity. It is also conventional in accordance with prior art processes to counterflow the rinse solutions from one rinse tank or reservoir to the next reservoir in a direction of progressively increasing rinse solution contamination. Fresh make-up water is added to the tank having the lowest degree of contamination and the effluent from the rinse tank having the highest degree of contamination is directed to a waste disposal treatment system. Systems of the foregoing type have been found to result in relatively high hydraulic loadings on liquid waste disposal systems, requiring the use of large amounts of chemical reagents and/or energy to effect a concentration and/or incineration thereof, detracting from the efficiency and economics of the process.
The foregoing problems are particularly pronounced during the bulk processing of relatively small workpieces which usually are placed within a barrel of other porous container and are conveyed through the individual treating stations in a prescribed processing sequence. The immersion of such bulk treating barrels in the rinse tanks filled with rinse solutions causes a surge which frequently results in an excessive degree of solution counterflow and fluctuations in composition, and also imposes a large and erratic hydraulic load on the waste disposal system.
The apparatus of the present invention overcomes the problems and disadvantages associated with liquid treating systems of the types heretofore known, providing for a substantial reduction in space requirements for a given production capacity, a more effective liquid treatment of workpieces and a lower rate and more uniform counterflow of the individual treating solutions, substantially reducing the hydraulic load imposed on waste disposal systems.